1. Field of the Invention
The present invention relates to a signal amplifying circuit, and more particularly, to a signal amplifying circuit capable of effectively suppressing noise by low speed of electric charge/discharge.
2. Description of the Prior Art
Chopping technology utilizes the switch to change orientation of the direct current (DC) offset and the low frequency noise relative to the signal, the direct current offset and the low frequency noise are transformed into high frequency interference, and the low-pass filter can be applied to eliminate the interference accordingly. An interior frequency bandwidth of the conventional chopping amplifier is greater than the chopping frequency to avoid insufficient settling time, and the chopping frequency has to be greater than signal frequency according to manufacture of the low-pass filter, so the conventional chopping amplifier has a drawback of high energy consumption. Besides, the low-pass filter of the conventional chopping amplifier is an internal capacitance of the circuit or an independent capacitance outside the circuit, which spends expensive material and manufacturing cost.